/Engine/Source/Developer/AssetTools/Public/IAssetTools.h
Flattens the maps for each selected package into one complete map to pass to the final copy function while checking for collisions
bool FlattenAdvancedCopyDestinations ( const [TArray](API\Runtime\Core\Containers\TArray)< [TMap](API\Runtime\Core\Containers\TMap)< [FString](API\Runtime\Core\Containers\FString), [FString](API\Runtime\Core\Containers\FString) >> & PackagesAndDestinations, [TMap](API\Runtime\Core\Containers\TMap)< [FString](API\Runtime\Core\Containers\FString), [FString](API\Runtime\Core\Containers\FString) > & FlattenedPackagesAndDestinations ) const